Magnetic resonance imaging (MRI) is a well known and established technique for imaging of soft tissue structures near and around bones and it is the most sensitive examination technique for spinal and joint problems. MRI is widely used to diagnose sports related injuries, especially those affecting the knee, shoulder, hip, elbow and wrist. In addition, MRI of the heart, aorta, coronary arteries and blood vessels is a fast, non-invasive tool for diagnosing coronary artery disease and heart problems. Organs of the chest and abdomen, including the lungs, liver, kidney, spleen, pancreas and abdominal vessels can also be examined in high detail with MRI, enabling the diagnosis and evaluation of tumors and functional disorders.
In MRI, radio frequency waves are directed at nuclei for example protons in a strong external magnetic field. The protons are first excited and then relaxed, emitting radio signals that can be detected and computer processed to form an image. Thereby, Magnetic Resonance (MR) radio frequency (RF) receive coils are necessary parts to receive said RF signals transmitted in a particular MR experiment. Thereby, the best antenna element location is close to the human body being scanned and therefore most of the MR receive coils are positioned on the patient by a scanner operator.
The actual workflow effectiveness of a particular coil implementation is very important to the MR scanner's operation since it determines in a large part the patient throughput of the MR scanner. Furthermore, a patient benefits from receive coils that have improved patient comfort which is mainly determined by efficient workflow (potentially a shorter or lesser claustrophobic experience) and an ergonomic design that reduces cable clutter, that adapts more flexible to different body shapes and is more lightweight.
Since MR receive coils or in general MR receive chains comprising the coils and various electronic components like amplifiers, switches etc., are highly sensitive to disturbances by external radio frequency waves, said MR receive chains have to be electromagnetically shielded which requires a spatial separation of the MR receive chains in an exam room and the control system in a separate technical room.
Current state of the art for MR receive chains feature a massive parallel analogue solution with many expensive analogue design elements such as RF switches, RF amplifiers, RF power supplies, RF cables and RF connectors etc. All these components are typically strewn over a distance of 10-20 meters between the receive chain in the exam room and analogue to digital converters in the technical room, which makes it one of the most complex and challenging aspects to cost effectively design and produce an MR scanner due to component spread and unwanted interactions between the many galvanic parts.
These problems become even more severe in the case of higher element counts in coils, i.e., coil systems comprising multiple individual coils which need to be effectively combined using a state of the art wire technology. Also, in MRI systems each galvanic wire needs trapping considerations and careful design must avoid image quality detrimental effects due to galvanic wiring coupling effects.
These problems can be overcome using a digital interface for a receiver coil unit. In this case, analogue to digital conversion is performed already within the receiver coil unit including the receive coil and the receiver. Connector and cable size and handling issues even for high element counts in coils can be overcome by effectively combining multiple elements information to just a few optical fibers or galvanic wires. Transferring RF and control and status signals digitally with optical fibers versus traditional galvanic wiring significantly reduces galvanic wiring overhead. This even enables a wireless transmission of said elements information. Comparing a digital interface for a coil to available technologies and components, the digital data transport and combined solution scores high on cost, size and power efficiency. An added benefit of a digital solution is that it allows additional control and acquisition features to be added in the coil with negligible cost, enabling for example tune transmit coils for self testing coils and control intensive solutions for more efficient coil power supplies etc.
WO 03/032002 A1 suggests a wireless remote control unit that operates in the radio frequency bandwidth which can be used for interfacing with a sequence control system and an image processing system from within a magnetic resonance suite in the presence of a magnetic field produced by a main magnet assembly.
U.S. Pat. No. 6,356,780 B1 discloses a technique for managing data relating to peripheral devices and subsystems in an imaging system including providing memory circuitry and, where desired, signal processing circuitry resident in the peripheral devices.
WO 2006/103591 A1 relates to a magnetic resonance imaging system, to a magnetic resonance imaging method for operating a magnetic resonance imaging system and a computer program for operating a magnetic resonance imaging system. In order to considerably reduce the number of cabling in a magnetic resonance imaging system, a magnetic resonance imaging system is suggested in which the number of cables are reduced by transferring the magnetic resonance signal data from the examination zone or from the vicinity of the examination zone to a remote signal processing unit outside the examination zone using a digital format. This allows the use of a simple digital connection, e.g., a single connection wire or like. A large bundle of coaxial cables is not needed, thus leading to a cheaper and more reliable magnetic resonance imaging system.
WO 2004/089211 A2 discloses a magnetic resonance imaging examination apparatus including a receiver assembly located in the vicinity of an examination zone for producing a signal in response to magnetic resonance signals for transmission to a signal processing system. To overcome problems associated with metallic cable connections between the signal generator and a signal processing unit and to overcome problems associated with existing non-metallic connections, the receiver assembly comprises a digitizer for generating a digital electromagnetic signal for transmission to the signal processing unit.
U.S. Pat. No. 6,339,717 B1 discloses a medical examination system, particularly a magnetic resonance system, comprising a host computer unit, a control computer unit and an image computer unit. Thereby, analogue to digital (AD) converters are arranged close to the radio frequency coils of the image signal reception system, where the examination system is fashioned as a magnetic resonance system. Thereby, the AD converter can be arranged in a connecting plug with which the signal line is connected to the radio frequency coils.
WO 2006/030331 A2 discloses a radio frequency receive coil which includes an antenna that is tuned to a magnetic resonance frequency to detect a magnetic resonance signal. Electronics disposed on with the antenna as a unitary structure include compression circuitry that comprises the magnetic resonance signal and a gain controlled by a gain control signal to produce a compressed magnetic resonance signal. Further, the electronics comprise an analogue to digital converter that digitizes a compressed magnetic resonance signal to produce a digitized compressed magnetic resonance signal.